Apple's new, freely-downloadable OS for the Mac is v10.14 and is called Mojave. As with every major release from the company, custom applications and OS-supplied developer tools may well have changed - and probably will need a bit of TLC to get them running again! Here's my list of updates that I've come across, and the remedial actions:
My big headache with this update is that the OS-supplied webserver doesn't run PHP 5.5 - and I actively develop a website that contains lots of deprecated functions (eg, mysql_connect). My solution to this is to instead develop that website inside a VM - and I've opted for a Homestead-configured vagrant machine running inside VirtualBox. This is a better way to develop anyway, as my development environment is now much closer to that of the live web server.
My software versioning tools - git and svn - are both working fine after the Mojave update.